1. Field of the Invention
The present invention relates to an apparatus for evaluating an image formation device, such as a laser printer and a copying machine. More particularly, the invention relates to a method of evaluating characteristics required of a light beam which is emitted from the write unit of an image formation device toward a latent image carrier, such as a photosensitive drum and a photosensitive belt. The invention also relates to a light beam characteristic evaluation apparatus that is employed for evaluating the characteristics, and further relates to an apparatus for adjusting a write unit by employing the evaluation method.
2. Description of the Related Art
Conventionally, an image forming device, such as a laser printer, a copying machine, and a facsimile device, performs writing on the surface of the photosensitive drum (latent image carrier) of an image forming unit by scanning the drum surface in both a horizontal scanning direction (i.e., main scanning direction) and a vertical scanning direction (i.e., sub-scanning direction) with a light beam emitted from a write unit, thereby forming an electrostatic latent image. In order to make the latent image visible and form a toner image, toner is caused to adhere to the surface of the photosensitive drum on which the latent image is formed. The toner image is transferred and fixed onto transfer paper. In this manner, an image is formed on the transfer paper.
The write unit is provided with an optical scanning system for scanning the surface of the photosensitive drum with a beam of light. The surface of the photosensitive drum is scanned in the horizontal scanning direction by the optical scanning system, while the surface is scanned in the vertical scanning direction by rotating the photosensitive drum.
In these image formation devices, incidentally, the characteristics required of the light beam of the write unit are evaluated in performing writing on the surface of the photosensitive drum which is a writing object.
For instance, in a copying machine, the image information on a manuscript is read in sequence and converted to a beam of light. In the case where the light beam writing position on the photosensitive drum surface deviates from a previously designed reference position, there arises a disadvantage that an image corresponding to the image information of a manuscript cannot be formed at the reference position. Particularly, in an image formation device, in which two laser light sources for emitting a beam of light are provided in the write unit and writing is performed on the photosensitive drum surface at two times the normal speed by scanning the photosensitive drum surface in the horizontal scanning direction concurrently with two light beams, if the writing position of one of the two light beams deviates from the writing position of the other light beam in the horizontal scanning direction, the image on a manuscript cannot be reproduced with high fidelity. Therefore, it is required to perform both the evaluation of the writing position of one light beam and the evaluation of the writing position of the other light beam.
In the case of a write unit which performs writing on a photosensitive drum by a single light beam, a writing position is computed for each surface of a polygon mirror constituting an optical scanning system. The object of evaluation in this case is both the position offset in the horizontal scanning direction (pitch fluctuation in the horizontal scanning direction) on each surface of the polygon mirror and the position offset in the vertical scanning direction (pitch fluctuation in the vertical scanning direction) on each surface of the polygon mirror.
In the case of a write unit which performs writing on a photosensitive drum by a plurality of multiplexed light beams, a pitch between light beams is also an object of evaluation in addition to the aforementioned evaluations.
Also, when two points on a manuscript in the horizontal scanning direction are extracted, two points on a copied image on transfer paper corresponding to the two points on the manuscript are extracted, and the distance between the two points on the manuscript is compared with the distance between the two points on the copied image, they must be equal to each other as long as copying is performed with equimagnification. If the distance between two points on a manuscript is not exactly equal to the distance between two points on a copied image, this will result in a magnification error. Since an image cannot be reproduced with high fidelity on transfer paper, performing the evaluation of a magnification error is required. In addition, in the case of enlargement and reduction, a ratio of a copied image formed on transfer paper to an image on a manuscript has to be equal to a desired magnification or demagnification ratio. If these ratio differ from each other, an image cannot be reproduced with high fidelity and therefore the evaluation of a magnification error will also be required.
Additionally, in the case where a left-side point and a right-side point on transfer paper are offset in the vertical scanning direction, it means that the scanning line has a tilt to the left or the right and therefore this scanning line tilt is also an object of evaluation.
Furthermore, assume that three points on a manuscript are extracted from left to right along the horizontal scanning direction and that the middle point is present at equal distances from the remaining two points. If the distance to the corresponding left-side point and the distance to the corresponding right-side point on the transfer paper are not equal with the corresponding middle point on the transfer paper as reference, a copied image will lack the balance between the right side and the left side. Therefore, it is also required to evaluate whether or not a distance from a middle point to a left-side point and a distance from a middle point to a right-side point are equal to each other.
In this case, if the difference between the writing position of the left-side point and the writing position of the middle point is not equal in the vertical scanning direction to the difference between the writing position of the right-side point and the writing position of the middle point, the scanning line will have a curve. Similarly, an image is not reproduced with high fidelity, so that it is also required to evaluate whether or not a scanning line has a curve.
Incidentally, a conventional apparatus for evaluating the characteristics of a light beam in the horizontal scanning direction is shown, for example, in FIG. 1 (see Japanese Laid-Open Patent Publication No. HEI 5-284293).
In the figure, reference numeral 1 denotes a write unit (optical unit). The write unit 1 is provided with a beam source (laser light source) 2, a rotatable polygon mirror 3, and an fxcex8 lens 4. The beam source (laser light source) consists of a semiconductor laser 2. The semiconductor laser 2 is modulated and driven by an optical analog modulator 5. The optical analog modulator 5 modulates the strength of laser light emitted from the semiconductor laser 2 in correspondence to a manuscript image. The laser light emitted from the semiconductor laser 2 is deflected by rotation of the polygon mirror 3.
A pair of spaced photoelectric conversion elements 7a and 7b are provided in the horizontal scanning direction on a photosensitive surface 6 equivalent to the surface of a photosensitive drum provided in an image forming unit. In order to enhance received-light position accuracy (writing position accuracy), light intercepting plates 8a and 8b with a pinhole (circular small hole) are provided directly before the photoelectric conversion elements 7a and 7b. Let the distance between this pair of pinholes be L.
If the polygon mirror 3 is rotated with the semiconductor laser 2 lit at all times during scanning and if the photosensitive surface 6 is scanned in the horizontal direction Q1 with the light beam P1, the first photoelectric conversion element 7a will first receive the light beam P1 and then the second photoelectric conversion element 7b will receive the light beam P1. From the difference between the light receiving times and the distance L, an actual scanning speed of the light beam P1 of this write unit 1 can be computed. When this actually measured scanning speed of the light beam P1 is faster or slower than a previously designed scanning speed, the writing position of the light beam P1 is offset from the writing reference position.
Hence, whether this actually measured scanning speed of the light beam is within the allowable error of the designed scanning speed is evaluated. In the case where the measured scanning speed has exceeded this allowable error, the revolution speed of the polygon mirror 3 is adjusted so that the scanning speed of the write unit is within the allowable error.
This conventional light beam characteristic evaluation apparatus cannot compute the writing position itself directly. If it is to be computed, time needs to be computed until an output signal is output from the second photoelectric conversion element 7b since an output signal was output from the first photoelectric conversion element 7a. In addition, an actual scanning speed needs to be computed by dividing the distance L with the computed time, and a computation for converting this scanning speed to a writing position is needed. Therefore, the procedure for computing the writing position becomes complicated. Also, the characteristics of the light beam to be evaluated are limited.
Next, in the case where the beam diameter of the light beam P1 on the surface of the photosensitive drum is offset from a previously designed value, the edge of an image formed on transfer paper will become dim, or cracks will occur in the scanning line, so that there is a disadvantage that picture quality will be degraded. Therefore, it is also required to evaluate the diameter or shape of the light beam on the scanned surface.
In a conventional method of evaluating the beam diameter of a light beam, a pinhole or a slit is provided at a position corresponding to the surface of a photosensitive drum, and a light receiving device is provided directly after the pinhole or the slit. With this arrangement, the beam diameter is measured in a stationary state. This conventional method, however, cannot measure the beam diameter in a scanning state.
Hence, in order to measure the beam diameter in a scanning state, a method of and an apparatus for evaluating the beam diameter of a light beam have been proposed (see Japanese Laid-Open Patent Publication No. HEI 4-351928). As shown in FIG. 2, a one-dimensional (1-D) charge coupled device (CCD) 9 is provided on the photosensitive surface 6 equivalent to the surface of the photosensitive drum. In the optical path of the light beam P1 traveling toward the 1-D CCD 9, an objective lens is provided for directing the light beam P1 onto the photosensitive surface 6. While the beam spot S of the light beam P1 is being moved in a direction of arrow Q1 along the horizontal scanning direction, the 1-D CCD 9 is scanned n times in a direction of arrow Q2. The light quantity signals of pixels C1 to Cn during a signal scan are integrated and stored in a storage circuit. By computing a signal from this storage circuit, the light beam diameter is computed.
Incidentally, in this conventional evaluation method, when the 1-D CCD 9 is moved once in the direction of arrow Q2 and then is moved again in the direction of arrow Q2, the 1-scan period t1 of the 1-D CCD 9 has elapsed. For this reason, the light beam P1 has moved in the horizontal scanning direction (direction of arrow Q1) for this 1-scan period t1. Therefore, this evaluation method is equivalent to the constitution in which n 1-D CCDs 9 are arranged at regular intervals with the beam spot S in a stationary state, as schematically shown in FIG. 3.
In this evaluation method, as evident in FIG. 3, the light beam P1 has moved in the horizontal scanning direction for the 1-scan period t1 of the 1-D CCD 9, so that the beam spot S is fetched in a thinned-out state in the 1-D CCD 9. Furthermore, during the scanning period xcex94t between the time that after a certain pixel Ci of the 1-D CCD 9 is scanned, the image information is read and the time that after the adjacent pixel Ci+1 is scanned, the image information is read, the light beam P1 also moves in the horizontal scanning direction (direction of arrow Q1). Therefore, this is equivalent to fetching an image of the beam spot S by obliquely scanning the 1-D CCD 9, so that an error easily comes to occur when the beam diameter is quantized. The evaluation error in this quantization of the beam diameter is increased as the scanning speed of the light beam P1 is increased.
The aforementioned conventional light beam characteristic evaluation method (beam diameter evaluation method), therefore, has the disadvantage that it is difficult to enhance the evaluation accuracy of the beam diameter.
As previously described, the characteristics required of the light beam are a writing position characteristic to a photosensitive drum surface, pitch fluctuation in a horizontal scanning direction, pitch fluctuation in a vertical scanning direction, a beam-to-beam pitch, a magnification error, right-left balance (magnification error deviation), a scanning line curvature, a light beam diameter, a beam shape, and so on. In prior art, since the beam characteristics are evaluated by exclusive evaluation apparatuses, the characteristic evaluation of the light beam becomes complicated and is not a synthetic evaluation under the same condition, so that there is a fear that reliability of evaluation will be slightly reduced.
Furthermore, for a method of evaluating a beam spot diameter or a beam spot shape, there is a demand for an even greater enhancement in the evaluation accuracy of the beam spot diameter or beam spot shape in a scanning state.
In addition, positioning of a reference position is required in order to perform these evaluations.
For instance, Japanese Laid-Open Patent Publication No. HEI 8-86616 discloses a three-dimensional (3-D) image measurement apparatus equipped with a computer. This measurement apparatus is provided with a laser head for emitting a cross-shaped slit light to an object of measurement having a 3-D shape. The laser head is provided on a laser head bed so that it is rotatable on the intersection of the crossed slit and movable in a right-and-left direction and an up-and-down direction. This measurement apparatus is further provided with a CCD camera for photographing the measurement object, an image processing section for processing an image signal photographed by the CCD camera, and a laser head operation control section. In this 3-D image measurement apparatus, the lens center of the CCD camera and the center portion of the point end of the laser head are located on the X axis of a 3-D absolute coordinate system, and the photographing surface of the CCD camera is arranged in parallel to the X-Y plane.
This image measurement apparatus merely performs positioning of the area-type CCD element of the CCD camera by adjusting the area-type CCD element at a specific position in correspondence to the photographing position of the area-type CCD element and does not specify a reference pixel as a reference position for measurement. For this reason, there is a problem in that the offset between the positions of the reference pixel and laser light cannot be accurately grasped.
It is a first object of the present invention to provide a light beam characteristic evaluation method and a light beam characteristic evaluation apparatus which are capable of evaluating all characteristics required of a light beam.
A second object of the present invention is to provide a light beam characteristic evaluation method and a light beam characteristic evaluation apparatus which are capable of evaluating the diameter or shape of a light beam accurately even during scanning in a horizontal scanning direction (i.e., main scanning direction).
A third object of the present invention is to provide a light beam characteristic evaluation apparatus which is capable of performing positioning of a reference position accurately.
A fourth object of the present invention is to provide an adjustment apparatus for a write unit which is suitable for performing adjustment on the basis of results evaluated by employing the light beam characteristic evaluation apparatus.
The foregoing objects are accomplished by providing a light beam characteristic evaluation method comprising the steps of: providing a light beam source for emitting a light beam which scans a surface linearly; lighting the light beam source during a scanning period equivalent to 1 dot during scanning; and evaluating characteristics required of the light beam.
The foregoing objects are also accomplished by providing a light beam characteristic evaluation method comprising the steps of: providing at least two light beam detection means spaced at a predetermined distance in a scanning direction of a surface to be scanned; emitting a light beam to the light beam detection means provided on a scanning start side by lighting a light beam source which is employed to scan the surface linearly during a scanning period equivalent to 1 dot during scanning; emitting a light beam to the light beam detection means provided on a scanning end side by lighting the light beam source during the scanning period after elapse of a light-off period computed from a previously designed scanning speed and the predetermined distance; and evaluating scanning characteristics required of the light beam, based on a detection result of the light beam detection means provided on the scanning start side and a detection result of the light beam detection means provided on the scanning end side.
The light beam source may be a semiconductor laser. The light beam detection means may be area-type solid-state imaging elements. The scanning characteristics may be evaluated by computing an offset quantity between the position of the light beam on an imaging surface of the solid-state imaging element and a previously designed reference position.
The scanning period and the light-off period may be defined based on a clock signal generated by a clock generator.
The light beam source may be lit until the number of clock pulses equivalent to 1 dot is counted and put out until the number of clock pulses equivalent to the light-off period is counted.
The foregoing objects are also accomplished by a light beam characteristic evaluation apparatus comprising: a light beam source for scanning a surface; a lighting control circuit for lighting the light beam source during a scanning period equivalent to 1 dot during scanning; light beam detection means provided on the surface for detecting a light beam emitted from the light beam source; and evaluation processing means for evaluating characteristics required of the light beam on the basis of a detection result of the beam detection means.
The light beam source may be assembled into a write unit equipped with an optical scanning system. The light beam detection means may be an area-type solid-state imaging element, and the evaluation processing means may compute a writing position as a characteristic required of the light beam on the basis of a detection result of the area-type solid-state imaging element.
The area-type solid-state imaging element may be provided with at least two area-type solid-state imaging elements spaced at a predetermined distance in a horizontal scanning direction. Computation means may be provided for computing a light-off period from a previously designed scanning speed and the predetermined distance. After the light beam has been emitted on the light beam detection means provided on a scanning start side, the light beam source may be put out during the light-off period, and the light beam source may be lit again during the scanning period equivalent to 1 dot after elapse of the light-off period, whereby the light beam may be emitted on the light beam detection means provided on a scanning end side, and based on detection results of the light beam detection means, scanning characteristics required of the light beam may be evaluated.
The foregoing objects are also accomplished by providing a light beam characteristic evaluation apparatus comprising: a laser light source provided in a write unit having an optical scanning system, the laser light source being employed for scanning a surface; a lighting control circuit for lighting the laser light source during a scanning period equivalent to 1 dot during scanning; an area-type solid-state imaging element provided on the surface for detecting a light beam emitted from the laser light source; and evaluation processing means for evaluating a writing position as a characteristic required of the light beam on the basis of a detection result of the area-type solid-state imaging element.
The area-type solid-state imaging element may be provided with at least two area-type solid-state imaging elements spaced at a previously designed predetermined distance in a horizontal scanning direction. The laser light source may be put out after it has been lit during a scanning period equivalent to 1 dot toward the area-type solid-state imaging element provided on the scanning start side, and the laser light source may be lit again during the scanning period after elapse of a light-off period computed from a previously designed scanning speed and the predetermined distance. The evaluation processing means may compute a magnification error, by comparing a distance between a writing position detected by the area-type solid-state imaging element on the scanning start side and a writing position detected by the area-type solid-state imaging element on the scanning end side with the predetermined distance.
The area-type solid-state imaging element may be provided with three area-type solid-state imaging elements spaced in a horizontal scanning direction, one of the three area-type solid-state imaging elements being provided at a center position, one of the remaining area-type solid-state imaging elements being provided on a scanning start side, the other being provided on a scanning end side, and the area-type solid-state imaging element at the center position being provided at equal distances from the opposite two area-type solid-state imaging elements. The laser light source may be put out after it has been lit during a scanning period equivalent to 1 dot toward the area-type solid-state imaging element provided on the scanning start side, and the laser light source may be lit again during the scanning period toward the remaining area-type solid-state imaging elements after elapse of a light-off period computed from a previously designed scanning speed and the predetermined distance. The evaluation processing means may evaluate right-left image balance as the scanning characteristics, by comparing a distance between a writing position detected by the area-type solid-state imaging element provided on the scanning start side and a writing position detected by the middle area-type solid-state imaging element with a distance between a writing position detected by the middle area-type solid-state imaging element and a writing position detected by the area-type solid-state imaging element provided on the scanning end side.
The aforementioned light beam characteristic evaluation apparatus may further comprise a clock pulse generator for defining both the scanning period equivalent to 1 dot and the light-off period. The light beam source may be lit until the number of clock pulses equivalent to 1 dot is counted and put out until the number of clock pulses equivalent to the light-off period is counted.
The aforementioned light beam characteristic evaluation apparatus may further comprise computation means for computing the light-off period from a previously designed scanning speed and the distance.
The write unit may be provided with synchronous sensors for determining a write timing period on the scanning start and scanning end sides in the horizontal scanning direction. The laser light source may be lit continuously until a light beam is detected by the synchronous sensor on the scanning start side, and it may be put out once for 1-dot lighting after the light beam has been detected by the synchronous sensor present on the scanning start side.
The laser light source may be provided with two laser light sources and wherein writing to the surface to be scanned is possible by two light beams.
The evaluation processing means may compute a beam-to-beam pitch, based on both a position at which the area-type solid-state imaging element received a light beam emitted from one of the two laser light sources and a position at which the area-type solid-state imaging element received a light beam emitted from the other of the two laser light sources, and the evaluation processing means may evaluate the degree of parallelization between two light beams by computing the beam-to-beam pitch at least two or more points spaced in the horizontal scanning direction.
The evaluation processing means may compute beam centers of the area-type solid-state imaging elements in a vertical scanning direction (i.e., sub-scanning direction), and may evaluate a scanning line curvature of the light beam, based on the computed beam centers.
The write unit may be equipped with a synchronous sensor for determining a write timing period on a scanning start side. The area-type solid-state imaging element may be movable in a horizontal scanning direction, and the lighting control circuit may be controlled so as to light the laser light source for a period of 1 dot after a light-off period, related to a distance between the synchronous sensor and the area-type solid-state imaging element, has elapsed.
The light-off period may be computed from the distance and a previously set theoretical scanning speed.
The foregoing objects are also accomplished by providing a light beam characteristic evaluation apparatus comprising: a light beam source for scanning a surface; a lighting control circuit for lighting the light beam source during a scanning period equivalent to 1 dot during scanning; an area-type solid-state imaging element provided on the surface for detecting a light beam from the light beam source lit by the lighting control circuit; and evaluation processing means for computing a diameter of the light beam on the surface.
The beam diameter may be evaluated at at least two places in a scanning direction.
The light beam may be moved linearly in a horizontal scanning direction, and the computation means may compute both a beam diameter in the horizontal scanning direction and a beam diameter in a vertical scanning direction perpendicular to the horizontal scanning direction.
The evaluation processing means may compute a center position of the light beam from both the beam diameter in the horizontal scanning direction and the beam diameter in the vertical scanning direction.
The evaluation processing means may compute a beam shape present on the surface from both the beam diameter in the horizontal scanning direction and the beam diameter in the vertical scanning direction.
The evaluation processing means may compute a center position of the light beam, by computing both an intensity distribution of the beam diameter in the horizontal scanning direction and an intensity distribution of the beam diameter in the vertical scanning direction on each pixel of the area-type solid-state imaging element.
The foregoing objects are also accomplished by providing a light beam characteristic evaluation apparatus for evaluating a beam diameter on a first surface scanned by a light beam emitted from a laser light source which is provided in a write unit having an optical scanning system and also which is employed to perform only writing on a latent image carrier, the light beam characteristic evaluation apparatus comprising: a lighting control circuit for lighting the laser light source during a scanning period equivalent to 1 dot during scanning; an area-type solid-state imaging element provided on a second surface equivalent to the first surface for detecting a light beam from the laser light source lit by the lighting control circuit; and evaluation processing means for computing a diameter of the light beam on the second equivalent surface.
The light beam may be moved linearly in a horizontal scanning direction, and the computation means may compute both a beam diameter in the horizontal scanning direction and a beam diameter in a vertical scanning direction perpendicular to the horizontal scanning direction.
The evaluation processing means may compute a center position of the light beam from both the beam diameter in the horizontal scanning direction and the beam diameter in the vertical scanning direction.
The write unit may be equipped with a synchronous sensor for determining a write timing period of the latent image carrier, and the optical scanning system may be equipped with an f xcex8 lens. The area-type solid-state imaging element may be arranged at an image height position equivalent to an optical axis position on the second equivalent surface, and the lighting control circuit may be controlled so as to light the laser light source for a period of 1 dot after a light-off period, related to a distance between the synchronous sensor and the area-type solid-state imaging element, has elapsed.
The evaluation processing means may evaluate a writing position, a magnification error, image balance, a scanning line curvature in a horizontal scanning direction, and a degree of parallelization of a light beam, based on the center position of the light beam.
The foregoing objects are also accomplished by providing a light beam characteristic evaluation method comprising the steps of: providing a light beam source for emitting a light beam which scans a surface linearly; lighting the light beam source during a scanning period equivalent to 1 dot during scanning; and computing a diameter or shape of the light beam.
The foregoing objects are also accomplished by providing an adjustment method comprising the steps of: providing a write unit incorporating an optical scanning system to form an electrostatic latent image on a surface of a latent image carrier by a light beam emitted from a laser light source; and moving the write unit relatively in a horizontal scanning direction against the latent image carrier in correspondence to an offset quantity of the light beam in the horizontal scanning direction, thereby adjusting the write unit.
The foregoing objects are also accomplished by providing an adjustment method comprising the steps of: providing a write unit incorporating an optical scanning system to form an electrostatic latent image on a surface of a latent image carrier by a light beam emitted from a laser light source; and moving the write unit relatively in a horizontal scanning direction against an image forming unit incorporating at least the latent image carrier in correspondence to an offset quantity of the light beam in the horizontal scanning direction, thereby adjusting the write unit.
The foregoing objects are also accomplished by an adjustment apparatus comprising: a write unit incorporating an optical scanning system to form an electrostatic latent image on a surface of a latent image carrier by a light beam emitted from a laser light source; an image forming unit incorporating at least the latent image carrier; and moving means for moving the write unit and the image forming unit relatively along a horizontal scanning direction in order to adjust an offset quantity of the light beam in the horizontal scanning direction.
The image forming unit may be provided with a developing unit.
The moving means may be constituted by a guide hole formed in a main body constitution wall of an image forming device and extending lengthwise in the horizontal scanning direction, and a support pin formed in either the write unit or the image forming unit and fitted into the guide hole.
The moving means may be constituted by an adjusting screw for moving either the write unit or the image forming unit in the horizontal scanning direction, and elastic means for urging either the write unit or image forming unit moved by the adjusting screw so that a point end of the adjusting screw abuts on the unit.
The moving means may be constituted by an adjusting screw for moving either the write unit or the image forming unit in the horizontal scanning direction and a boss portion provided in either the write unit or image forming unit moved by the adjusting screw, the adjusting screw meshing with the boss portion.
The foregoing objects are also accomplished by an adjustment method wherein a write unit, incorporating an optical scanning system to form an electrostatic latent image on a surface of a latent image carrier by a light beam emitted from a laser light source, is adjusted by moving the write unit relatively in a vertical scanning direction against the latent image carrier in correspondence to an offset quantity of the light beam in the vertical scanning direction, the vertical scanning direction being defined as a direction perpendicular to both a traveling direction of a light beam which is incident from the write unit toward the image forming unit and a horizontal direction.
The foregoing objects are also accomplished by an adjustment method wherein a write unit, incorporating an optical scanning system to form an electrostatic latent image on a surface of a latent image carrier by a light beam emitted from a laser light source, is adjusted by moving the write unit relatively in a vertical scanning direction against an image forming unit incorporating at least the latent image carrier in correspondence to an offset quantity of the light beam in the vertical scanning direction, the vertical scanning direction being defined as a direction perpendicular to both a traveling direction of a light beam which is incident from the write unit toward the image forming unit and a horizontal direction.
The foregoing objects are also accomplished by an adjustment apparatus comprising: a write unit incorporating an optical scanning system to form an electrostatic latent image on a surface of a latent image carrier by a light beam emitted from a laser light source; an image forming unit incorporating at least the latent image carrier; and moving means for moving the write unit and the image forming unit relatively along a vertical scanning direction defined as a direction perpendicular to both a traveling direction of a light beam which is incident from the write unit toward the image forming unit and a horizontal direction in order to adjust an offset quantity of the light beam in the vertical scanning direction.
The image forming unit may be provided with a developing unit.
The moving means may be constituted by a guide hole formed in a main body constitution wall of an image forming device and extending lengthwise in the vertical scanning direction, and a support pin formed in either the write unit or the image forming unit and fitted into the guide hole.
The moving means may be constituted by an adjusting screw for moving either the write unit or the image forming unit in the vertical scanning direction and elastic means provided in either the write unit or image forming unit moved by the adjusting screw, the elastic means being used for urging the moved unit so that a point end of the adjusting screw abuts on the unit.
The moving means may be constituted by an adjusting screw for moving either the write unit or the image forming unit in the vertical scanning direction and a boss portion provided in either the write unit or image forming unit moved by the adjusting screw, the adjusting screw meshing with the boss portion.
The foregoing objects are also accomplished by an adjustment method comprising the steps of: providing a write unit which incorporates both an optical scanning system and a synchronous sensor for determining a write timing period with respect to a latent image carrier in order to form an electrostatic latent image on a surface of the latent image carrier by a light beam emitted from a laser light source; and moving the synchronous sensor in a horizontal direction in correspondence to an offset quantity of the light beam of the write unit with respect to the latent image carrier in the horizontal scanning direction, thereby adjusting the offset quantity.
The foregoing objects are also accomplished by an adjustment apparatus comprising: a write unit incorporating both an optical scanning system and a synchronous sensor for determining a write timing period with respect to a latent image carrier in order to form an electrostatic latent image on a surface of the latent image carrier by a light beam emitted from a laser light source; and moving means for moving the synchronous sensor in a horizontal scanning direction in order to adjust an offset quantity of the light beam of the write unit with respect to the latent image carrier in the horizontal scanning direction.
The moving means may be constituted by a movable body for holding the synchronous sensor, a guide shaft for guiding the movable body in the horizontal scanning direction, an adjusting screw for moving the movable body by its point end portion abutting on the movable body, and means for urging the movable body in a direction which abuts on the point end portion of the adjusting screw.
The foregoing objects are also accomplished by a light beam characteristic evaluation method comprising the steps of: lighting a laser light source of a light beam which is employed to scan a surface linearly during a scanning period equivalent to 1 dot; moving an area-type solid-state imaging element which detects the light beam in order along a traveling direction of the light beam with the surface as a reference position; and obtaining a beam image at each position by the area-type solid-state imaging element.
Based on each beam image obtained by the area-type solid-state imaging element at each position in the traveling direction of the light beam, a beam diameter may be computed at the each position of the light beam, whereby a beam diameter with respect to a depth direction may be evaluated.
From the beam diameter and a depth, a depth curve representative of a relation of the beam diameter to the depth is computed, a beam waist position may be specified based on the depth curve, and from a difference between the beam waist position and the reference position, a beam waist position correction quantity may be computed.
The foregoing objects are also accomplished by a light beam characteristic evaluation apparatus comprising: a light beam source for emitting a light beam which scans a surface linearly; a 1-dot lighting control circuit for lighting the light beam source during a scanning period equivalent to 1 dot; an area-type solid-state imaging element for detecting the light beam, the element being movable in a traveling direction of the light beam with the surface as a reference position; and evaluation processing means for computing a beam diameter at each position in the traveling direction of the light beam, based on the light beam detected by the area-type solid-state imaging element.
The evaluation processing means may compute a depth curve representative of a relation of the beam diameter to a depth from the beam diameter and depth and specify a beam waist position on the basis of the depth curve. Furthermore, the evaluation processing means may compute a beam waist position correction quantity from a difference between the beam waist position and the reference position.
The foregoing objects are also accomplished by a light beam characteristic evaluation apparatus comprising: a write unit with an optical scanning system; a light beam source for emitting a light beam which scans a surface linearly, the light beam source being provided in the write unit; a 1-dot lighting control circuit for lighting the light beam source during a scanning period equivalent to 1 dot; an area-type solid-state imaging element for detecting the light beam, the element being movable in a traveling direction of the light beam with the surface as a reference position; and evaluation processing means for computing a beam diameter at each position in the traveling direction of the light beam, based on the light beam detected by the area-type solid-state imaging element; the write unit being equipped with a synchronous sensor for determining a write timing period on a scanning start side in a horizontal scanning direction; the laser light source being lit continuously until the light beam is detected by the synchronous sensor present on a scanning start side and also being put out once for 1-dot lighting after the light beam has been detected by the synchronous sensor present on the scanning start side; and the 1-dot lighting control circuit being controlled so that the laser light source is lit after elapse of the write timing period.
The aforementioned light beam characteristic evaluation apparatus may further comprise: computation means for computing the write timing period from both a distance in a horizontal direction between the synchronous sensor and the area-type solid-state imaging element and a previously designed scanning speed; and a clock pulse generator for defining both the scanning period equivalent to 1 dot and the write timing period. The light beam source is lit until a light beam is detected by the synchronous sensor, is put out until the number of clock pulses equivalent to the write timing period is counted since the synchronous sensor detected the light beam, and is lit by the 1-dot lighting control circuit until the number of clock pulses equivalent to 1 dot is counted.
The foregoing objects are also accomplished by an adjustment method wherein at least either an image forming unit or a write unit is moved so that a space therebetween is increased or decreased, in order to adjust an optical path length between a laser light source and a writing object surface of the image forming unit and based on a beam waist position correction quantity obtained by a light beam characteristic evaluation method comprising the steps of: (a) lighting the laser light source of a light beam which is employed to scan the writing object surface of the image forming unit linearly during a scanning period equivalent to 1 dot; (b) moving an area-type solid-state imaging element which detects the light beam in order along a traveling direction of the light beam with the writing object surface as a reference position, thereby obtaining a beam image at each position by the area-type solid-state imaging element; (c) based on each beam image obtained by the area-type solid-state imaging element at each position in a traveling direction of the light beam, computing a beam diameter at the each position of the light beam and thereby computing a beam diameter with respect to a depth direction; (d) from the beam diameter and a depth, computing a depth curve representative of a relation of the beam diameter to the depth; (e) specifying a beam waist position on the basis of the depth curve; and (f) from a difference between the beam waist position and the reference position, computing the beam waist position correction quantity.
The foregoing objects are also accomplished by an adjustment apparatus which comprises optical path length adjustment means for moving at least either an image forming unit or a write unit so that a space therebetween is increased or decreased, in order to adjust an optical path length between a laser light source and a writing object surface of the image forming unit and based on a beam waist position correction quantity obtained by a light beam characteristic evaluation method comprising the steps of: (a) lighting the laser light source of a light beam which is employed to scan the writing object surface of the image forming unit linearly during a scanning period equivalent to 1 dot; (b) moving an area-type solid-state imaging element which detects the light beam in order along a traveling direction of the light beam with the writing object surface as a reference position, thereby obtaining a beam image at each position by the area-type solid-state imaging element; (c) based on each beam image obtained by the area-type solid-state imaging element at each position in a traveling direction of the light beam, computing a beam diameter at the each position of the light beam and thereby computing a beam diameter with respect to a depth direction; (d) from the beam diameter and a depth, computing a depth curve representative of a relation of the beam diameter to the depth; (e) specifying a beam waist position on the basis of the depth curve; and (f) from a difference between the beam waist position and the reference position, computing the beam waist position correction quantity.
In order to change an optical path length between a surface of a latent image carrier of the image forming unit and the write unit, the optical path length adjustment means may be constituted by a guide hole formed in a main body constitution wall of an image forming device and a guide pin formed in either the write unit or the image forming unit and fitted into the guide hole.
The foregoing objects are also accomplished by an adjustment method wherein an optical path length between a laser light source and a surface to be scanned is adjusted based on a beam waist position correction quantity obtained by a light beam characteristic evaluation method comprising the steps of: (a) lighting the laser light source of a light beam which is employed to scan the surface linearly during a scanning period equivalent to 1 dot; (b) moving an area-type solid-state imaging element which detects the light beam in order along a traveling direction of the light beam with the writing object surface as a reference position, thereby obtaining a beam image at each position by the area-type solid-state imaging element; (c) based on each beam image obtained by the area-type solid-state imaging element at each position in a traveling direction of the light beam, computing a beam diameter at the each position of the light beam and thereby computing a beam diameter with respect to a depth direction; (d) from the beam diameter and a depth, computing a depth curve representative of a relation of the beam diameter to the depth; (e) specifying a beam waist position on the basis of the depth curve; and (f) from a difference between the beam waist position and the reference position, computing the beam waist position correction quantity.
The foregoing objects are also accomplished by an adjustment apparatus which comprises optical path length adjustment means for adjusting an optical path length between a laser light source and a surface to be scanned, based on a beam waist position correction quantity obtained by a light beam characteristic evaluation method comprising the steps of: (a) lighting the laser light source of a light beam which is employed to scan the surface linearly during a scanning period equivalent to 1 dot; (b) moving an area-type solid-state imaging element which detects the light beam in order along a traveling direction of the light beam with the writing object surface as a reference position, thereby obtaining a beam image at each position by the area-type solid-state imaging element; (c) based on each beam image obtained by the area-type solid-state imaging element at each position in a traveling direction of the light beam, computing a beam diameter at the each position of the light beam and thereby computing a beam diameter with respect to a depth direction; (d) from the beam diameter and a depth, computing a depth curve representative of a relation of the beam diameter to the depth; (e) specifying a beam waist position on the basis of the depth curve; and (f) from a difference between the beam waist position and the reference position, computing the beam waist position correction quantity.
The laser light source may be equipped with a semiconductor laser for emitting a light beam, a collimator lens for collimating the light beam, and a lens barrel for holding the collimator lens. The lens barrel may be formed with a first screw portion along an optical axis direction. The constitution wall of the write unit may be formed with a second screw portion at a position at which the lens barrel is arranged, the first screw portion meshing with the second screw portion. The optical path length adjustment means may be constituted by the first and second screw portions.
The foregoing objects are also accomplished by a light beam characteristic evaluation apparatus which is employed in a method of evaluating characteristics required of a light beam by forming the light beam on an area-type imaging element installed on a first surface equivalent to a second surface to be scanned, the light beam being emitted from a laser light source which is employed to scan the second surface linearly, the light beam characteristic evaluation apparatus comprising: a reference laser light source for determining previously designed reference positions of the light beam present on the second surface in horizontal and vertical scanning directions; a holder member for holding the reference laser light source; an angular position determination member for holding the holder member so that the holder member is rotatable and determining a rotational angular position of the reference laser light source; and a positioning reference base for positioning the angular position determination member so that a center of rotation of the holder member is aligned with a previously designed emission line of the light beam; wherein a reference pixel equivalent to the reference position on the area-type imaging element is specified, by rotating the holder member on the center of rotation and receiving a reference light beam emitted from the reference laser light source at at least two rotational angular positions with the area-type imaging element.
The positioning reference base may extend in the horizontal scanning direction.
The reference laser light source may be a semiconductor laser.
The laser light source may be provided in a write unit incorporating an optical scanning system.
The evaluation may be performed by lighting the laser light source during a scanning period equivalent to 1 dot during scanning.
The foregoing objects are also accomplished by a light beam characteristic evaluation apparatus which is employed in a method of evaluating characteristics required of a light beam by forming the light beam on an area-type imaging element installed on a first surface equivalent to a second surface to be scanned, the light beam being emitted from a laser light source provided in a write unit having an optical scanning system for linearly scanning the second surface of a latent image carrier provided in an image forming unit, the light beam characteristic evaluation apparatus comprising: a positioning member for positioning the write unit with respect to the image forming unit; a reference laser light source for determining previously designed reference positions of a light beam on the second surface in horizontal and vertical scanning directions, the light beam being emitted from the laser light source; a holder member for holding the reference laser light source; an angular position determination member for holding the holder member so that the holder member is rotatable and determining a rotational angular position of the reference laser light source; and a positioning reference base for positioning the angular position determination member so that a center of rotation of the holder member is aligned with a previously designed emission line of the light beam emitted from the write unit, the positioning reference base being provided in a positioning base; wherein a reference pixel equivalent to the reference position on the area-type imaging element is specified, by rotating the holder member on the center of rotation and receiving a reference light beam emitted from the reference. laser light source at at least two rotational angular positions with the area-type imaging element.
The rotational angular positions may be symmetrical positions spaced 180 degrees.
The angular position determination member may be provided on the positioning reference base so that it can be relocated in the horizontal scanning direction.
The aforementioned light beam characteristic evaluation apparatus may further comprise adjustment means for adjusting an imaging surface of the area-type imaging element so that the imaging surface is located at the first surface.
The foregoing objects are also accomplished by a light beam characteristic evaluation apparatus which is employed in an evaluation method comprising the steps of: lighting a laser light source during a scanning period equivalent to 1 dot during scanning, the laser light source being provided in a write unit having an optical scanning system for linearly scanning a first surface of a latent image carrier of an image forming unit; forming the light beam on at least two or more area-type imaging elements spaced in a horizontal scanning direction and provided on a second surface equivalent to the first surface to be scanned; and evaluating characteristics required of the light beam; the light beam characteristic evaluation apparatus comprising: a positioning member for positioning the write unit with respect to the image forming unit; a reference laser light source for determining previously designed reference positions of a light beam on the first surface in horizontal and vertical scanning directions, the light beam being emitted from the laser light source; a cylindrical holder member for holding the reference laser light source; angular position determination members for determining a rotational angular position of the reference laser light source, the determination members having a circular fitting hole into which the cylindrical holder member is rotatably fitted; and a positioning reference base for positioning the angular position determination members so that a center of rotation of the cylindrical holder member is aligned with a previously designed emission line of the light beam emitted from the write unit, the positioning reference base being provided in a positioning base; wherein a reference pixel equivalent to the reference position on the area-type imaging element is specified, by rotating the cylindrical holder member and receiving a reference light beam emitted from the reference laser light source at at least two rotational angular positions with the area-type imaging elements.
The angular position determination member may be provided with an engagement pin and the cylindrical holder member is provided with an engagement hole which engages with the engagement pin.
The rotational angular positions may be symmetrical positions spaced 180 degrees.
The angular position determination member may be provided in the positioning reference base so that it can be relocated in the horizontal scanning direction.
The angular position determination members may be spaced in the horizontal scanning direction and provided in correspondence to the area-type imaging elements.
Once a reference pixel of a certain area-type imaging element has been specified by rotating the cylindrical holder member, the specification of reference pixels of the remaining area-type imaging elements is performed without rotating the cylindrical holder member.